Mass marketing of retail goods requires the repetitious marking of individual items with price or other information. Marks may either be directly stamped on the goods or first imprinted on adhesive labels and the labels affixed to the goods. The subject marking tool is of the latter category and contains a supply of adhesive labels and a printing head with a variety of selectable characters which may be impressed on the labels.
Although numerous marking tools of this type are presently available, they are cumbersome and expensive. A primary problem in constructing a label marker is in accurately advancing the labels to printing position. Some devices employ friction drive rollers to advance labels. However, when the rollers pull on silicone coated backing tape of the adhesive labels, silicone eventually coats the rubber rollers and the rollers cease to operate properly. Other devices employ conveyer belts or shuttle mechanisms to advance the labels but the very complexity of these mechanisms often leads to their high cost and inefficiency.
The subject marking tool carries a supply of adhesive labels in a molded plastic casing having a pistol grip and trigger. The trigger is directly connected to the printing head by a long pivot arm. Connected to the pivot arm by a ratchet and pawl assembly is a tape drive mechanism which advances the labels by engaging drive teeth in perforation slits in the backing tape of the adhesive labels. The positive drive mechanism for advancing the tape insures that the printing head properly marks each label without drifting.
The positive drive mechanism to which the present improvements relate is described in the application of William Martin, entitled "Merchandise Marking Gun," Ser. No. 361,480, filed May 18, 1973, now U.S. Pat. No. 3,800,701, and continued from an application of the same title, Ser. No. 134,346, filed on Apr. 15, 1971, (now abandoned) and assigned to the assignee of the present application.
This invention relates to an improved drive mechanism having a cam operated pressure shoe for controlled tension in the backing tape and a retractable guide member which when engaged maintains the backing tape against the drive wheel in engagement with the drive teeth and when retracted allows the backing tape to be threaded around the drive wheel.
The cam operated pressure shoe is selectively depressed against the label tape on a printing guide plate during label transport to impart a momentary increase in tension in the backing tape at the point a label approaches a sharp reverse or switchback in the direction the backing tape advances through the marking gun. This temporary increased tension materially aids the separation of the label from the backing tape and is particularly effective when the label has lost its original stiffness through absorption of atmospheric moisture.
Additionally, the cam system allows the use of tamper proof labels with partial cross cuts that cause tearing of the label when an attempt is made to remove the label from the article to which is is attached. Such tamper proof labels require a more controlled handling by a transport mechanism to prevent jamming of these sensitive labels in the marking gun caused by incomplete separation from the backing tape.
The retractable guide member comprises a guide member which maintains the backing tape against the drive wheel such that the teeth pass through perforations in the backing tape. Since the marking gun of the type described is used by general clerical personnel, threading of the tape when replacing an exhausted roll must be accomplished quickly and easily without the use of tols. To facilitate threading, the guide member is retracted from the drive wheel by a thumb trigger which projects through the casing of the marking gun for threading of the tape without interference by the drive teeth.